This invention relates generally to the treatment of diseased or traumatized intervertebral discs, and more particularly, to transplantation of transplantation of dehydrated tissue including nucleus pulposis in conjunction with such treatment.
Intervertebral discs provide mobility and a cushion between the vertebrae. At the center of each disc is the nucleus pulposus which, in the adult human, is composed of cells and an insoluble extracellular matrix which is produced by the nucleus itself. The extracellular matrix is composed of collagen, proteoglycans, water, and noncollagenous proteins. The nucleus pulposus is surrounded by the annulus fibrosis, which is composed of cells (fibrocyte-like and chondrocyte-like), collagen fibers, and non-fibrillar extracellular matrix. The components of the annulus are arranged in 15-25 lamellae around the nucleus pulposus.
The cells of the nucleus pulposus have chondrocyte-like features. In an adult human, the cells of the nucleus pulposis obtain nutrients and eliminate waste by diffusion through blood vessels in the endplates of the vertebrae adjacent to the disc. Blood vessels do not course into the nucleus pulposis. The relative vascular isolation of the nucleus pulposis imparts isolation of nucleus pulposis cells from the body""s immune system.
To date, the treatment of degenerative disc disease has relied for the most part on eliminating the defective disc or disc function. This may be accomplished by fusing the vertebra on either side of the disc. In terms of replacement, most prior-art techniques use synthetic materials to replace the entire disc or a portion thereof. My pending U.S. patent application Ser. No. 09/415,382 discloses disc replacement methods and apparatus using synthetic materials.
Unfortunately, disc replacement using synthetic materials does not restore normal disc shape, physiology, or mechanical properties. Synthetic disc replacements tend to wear out, resulting in premature failure. The problems associated with the wear of prosthetic hip and knees are well known to those skilled in orthopedic surgery. The future of treating degenerative disc disease therefore lies in treatments which preserve disc function. If disc function could be restored with biologic replacement or augmentation, the risk of premature wearout would be minimized, if not eliminated.
This invention is directed to a method of treating a diseased or traumatized intervertebral disc through the transplantation of one or more dehydrated biologic tissues into the disc space. In the preferred embodiment, dehydrated nucleus tissue is used, which may be combined with extracellular matrix materials.
Broadly according to the method, live biologic tissue is harvested from a human or animal donor. The tissue is dehydrated, after which the harvested tissue is introduced into the disc being treated through a hole formed in the annulus fibrosis. Dehydration allows the insertion of the transplanted cells and/or tissue through a smaller annular hole. Dehydration also decreases the volume of the material transferred, thus allowing the surgeon to insert more into the disc space. Once in the body, the materials hydrate by imbibing fluid from the surrounding area. In the case of nucleus pulposis tissue, the subsequent hydration helps to restore disc height and help prevent extrusion of disc material through the hole in the annulus.
A preferred embodiment includes the step of harvesting nucleus pulposis cells, with or without extracellular matrix material, dehydrating and morselizing the cells and/or tissues. A passageway is formed through the annulus fibrosis, and the dehydrated components are introduced into the disc through the passageway using, for example, a needle and syringe or small cannula. Alternatively the step of transplanting may include percutaneously or laparoscopically injecting the dehydrated constituents into the disc being treated. Nucleus cells are added to the dehydrated tissue at the time of insertion.
One or more therapeutic substances may be added, including culture media, growth factors, differentiation factors, hydrogels, polymers, antibiotics, anti-inflammatory medications, or immunosuppressive medications. These additional substances may or may not be dehydrated as well, depending upon efficacy, initial versus final volume, and so forth.